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A Scala ORM and DSL for talking with Databases using minimum verbosity and maximum type safety
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/*******************************************************************************
 * Copyright 2010 Maxime Lévesque
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ***************************************************************************** */
package org.squeryl

import logging.StatisticsListener
import org.squeryl.internals._
import collection.mutable.ArrayBuffer
import java.sql.{SQLException, ResultSet, Statement, Connection}


class Session(val connection: Connection, val databaseAdapter: DatabaseAdapter, val statisticsListener: Option[StatisticsListener] = None) {

  def bindToCurrentThread = Session.currentSession = Some(this)

  def unbindFromCurrentThread = Session.currentSession = None

  private var _logger: String => Unit = null

  def logger_=(f: String => Unit) = _logger = f

  def setLogger(f: String => Unit) = _logger = f

  def isLoggingEnabled = _logger != null

  def log(s:String) = if(isLoggingEnabled) _logger(s)

  var logUnclosedStatements = false

  private val _statements = new ArrayBuffer[Statement]

  private val _resultSets = new ArrayBuffer[ResultSet]

  private [squeryl] def _addStatement(s: Statement) = _statements.append(s)

  private [squeryl] def _addResultSet(rs: ResultSet) = _resultSets.append(rs)

  def cleanup = {
    _statements.foreach(s => {
      if (logUnclosedStatements && isLoggingEnabled && !s.isClosed) {
        val stackTrace = Thread.currentThread.getStackTrace.map("at " + _).mkString("\n")
        log("Statement is not closed: " + s + ": " + System.identityHashCode(s) + "\n" + stackTrace)
      }
      Utils.close(s)
    })
    _statements.clear
    _resultSets.foreach(rs => Utils.close(rs))
    _resultSets.clear
  }

  def close = {
    cleanup
    connection.close
  }
}

trait SessionFactory {
  def newSession: Session
}

object SessionFactory {

  /**
   * Initializing concreteFactory with a Session creating closure enables the use of
   * the 'transaction' and 'inTransaction' block functions 
   */
  var concreteFactory: Option[()=>Session] = None

  /**
   * Initializing externalTransactionManagementAdapter with a Session creating closure allows to
   * execute Squeryl statements *without* the need of using 'transaction' and 'inTransaction'.
   * The use case for this is to allow Squeryl connection/transactions to be managed by an
   * external framework. In this case Session.cleanupResources *needs* to be called when connections
   * are closed, otherwise statement of resultset leaks can occur. 
   */
  var externalTransactionManagementAdapter: Option[()=>Option[Session]] = None

  def newSession: Session =
      concreteFactory.getOrElse(
        org.squeryl.internals.Utils.throwError("org.squeryl.SessionFactory not initialized, SessionFactory.concreteFactory must be assigned a \n"+
              "function for creating new org.squeryl.Session, before transaction can be used.\n" +
              "Alternatively SessionFactory.externalTransactionManagementAdapter can initialized, please refer to the documentation.")
      ).apply        
}

object Session {

  /**
   * Note about ThreadLocals: all thread locals should be .removed() before the
   * transaction ends.
   * 
   * Leaving a ThreadLocal inplace after the control returns to the user thread
   * will pollute the users threads and will cause problems for e.g. Tomcat and
   * other servlet engines.
   */
  private val _currentSessionThreadLocal = new ThreadLocal[Session]
  
  def create(c: Connection, a: DatabaseAdapter) =
    new Session(c,a)  

  def currentSessionOption: Option[Session] = {
    Option(_currentSessionThreadLocal.get) orElse {
      SessionFactory.externalTransactionManagementAdapter flatMap { _.apply() }
    }
  }

  def currentSession: Session =
    if(SessionFactory.externalTransactionManagementAdapter != None) {
      SessionFactory.externalTransactionManagementAdapter.get.apply getOrElse org.squeryl.internals.Utils.throwError("SessionFactory.externalTransactionManagementAdapter was unable to supply a Session for the current scope")
    }
    else currentSessionOption.getOrElse(
      org.squeryl.internals.Utils.throwError("No session is bound to current thread, a session must be created via Session.create \nand bound to the thread via 'work' or 'bindToCurrentThread'\n Usually this error occurs when a statement is executed outside of a transaction/inTrasaction block"))

  def hasCurrentSession =
    currentSessionOption != None

  def cleanupResources =
    currentSessionOption foreach (_.cleanup)

  private def currentSession_=(s: Option[Session]) = 
    if (s == None) {
      _currentSessionThreadLocal.remove()        
    } else {
      _currentSessionThreadLocal.set(s.get)
    }
  
}